The single-atom metal M-N-C catalyst displays a certain activity for the aerobic oxidation. A single-atom M-N3/C (M = Sc ∼ Cu) surface was modeled as a M-N-C catalyst, in which a metal adatom was located on a monovacancy defective nitrogen-doped graphene. Over M-N3/C (M = Sc ∼ Cu), the activation mechanism has been theoretically studied at the GGA-PBE/DNP level. The stability of M-N3/C increases as Cu Ti > V > Cr > Mn > Fe > Co > Ni > Cu, which have a negative correlation with either charge or the energy level difference (ɛd) for the center of the d-bands relative to the Fermi level of metal-site. Thermodynamically, the possibility for the dissociation of O2 decreases as Mn > Ti > Cu > Ni > Cr > V = Fe > Co > Sc.
